This invention relates to a method for producing a carbocyclic compound by extrusion of a sulfur atom from a cyclic sulfide.
Carbocyclic compounds are produced by a variety of synthetic pathways. Many examples are known of carbocyclic ring contraction reactions, wherein a carbon atom which is part of a ring is extruded, to produce a smaller carbocyclic ring containing one or more fewer carbon atoms. Such reactions are summarized by Redmore et al., in Advances in Alicyclic Chemistry, Hart et al., Eds., Vol. 3, 1-138 (Academic Press, 1971). It is known that when .alpha.-halo sulfones are treated with base, olefins are produced, with extrusion of sulfur dioxide. A reductive extrusion of sulfur from episulfides to form olefins is also known. However, extrusion of sulfur in a single step from a cyclic sulfide, to produce a carbocyclic ring having a carbon-carbon single bond linking those carbons formerly joined to sulfur, is unprecedented.
The method of the present invention is particularly suitable for the production of substituted or unsubstituted cyclobutanes. Known methods for synthesizing cyclobutanes include the condensation of 1,3-dibromopropanes with malonic ester or other activated methylene, dimerization of ketenes, allenes, acrylonitrile and polyfluoroethylenes. In addition, photoaddition of olefins to unsaturated ketones has been used to build a cyclobutane ring onto a conjugated double bond.
Cyclobutane itself may be produced from the malonic ester condensation product by decarboxylation, reduction to cyclobutylmethanol and catalytic dehydroxymethylation, as taught in U.S. Pat. No. 2,753,380 to Pines et al. Alternatively, the photolysis of cyclopentanone produces a minor percentage of cyclobutane and a major percentage of ethylene, as taught in U.S. Pat. No. 2,414,880 to Kistiakowsky et al. 1,4-dibromobutane has been coupled with lithium amalgam to give cyclobutane, by Connor et al., Tet. Let, 1967, 4925.
The present inventors investigated the reaction of ozone and thiirane, and found that this system rapidly converts to an ozone-olefin-SO.sub.2 system. Furthermore, the ethylene then reacts with the ozone to produce other radicals, especially OH radicals, which are the principal chain carriers of the reaction, as reported in Chem. Phys. Let., 72, 74 (1980). The authors suggested that analogous results might be anticipated for the reaction of ozone with the homologous episulfides and possibly also for higher cyclic sulfides. Finally, Dorer et al., J. Phys. Chem., 84, 1302 (1980), reported a study of the gas phase photolysis of tetramethylene sulfoxide. The photolysis was affected at various excitation wave lengths, including mercury sensitization, and a variety of products were observed, including cyclobutane, although cyclobutane was never the exclusive product. The authors maintain consistently that cyclobutane is produced through a tetramethylene diradical, a position which also requires that ethylene be produced concomitantly.
There is no suggestion in the combined teachings of the prior art references that a non-photolytic process could convert a cyclic sulfide to a carbocyclic compound with extrusion of sulfur, where the carbocyclic ring is substantially the exclusive product, and where substantially no olefin is formed. Moreover, in the case of cyclobutane, the intermediacy of a tetramethylene diradical was uniformly considered to be involved in any reaction wherein a cyclic ketone or sulfur-containing precursor is reacted to eliminate sulfur and to produce hydrocarbon products, so that olefinic products were always expected as well.
Cyclobutane is useful as a detection compound in actinometry, the measurement of light intensity, in the vacuum ultraviolet region, in liquid phase. It forms ethylene with a quantum yield of 2. Furthermore, compounds containing cyclobutane rings have been shown to be useful in applications as diverse as pharmaceuticals, e.g., cyclobutane analogs of prostanoids, anesthetics, progestational agents, antipyretics, antihypertensives, and in perfume and dentifrice preparations. The method of the invention is also useful in providing an alternative pathway to fused, bridged and/or spirocyclic ring systems of interest to both synthetic chemists and theoreticians.
A need therefore continues to exist for a simple and practical method of producing carbocyclic compounds, especially compounds containing a cyclobutane ring.